• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.205-205
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• 2006

Adsorption behaviors of positively charged matrix (PAH) onto negatively charged probe (sulfate PS particle) were investigated using DLS (dynamic light scattering) and FPR (fluorescence photobleaching recovery) as view points of matrix and salt concentration. The system experienced sharp decrease of diffusion (flocculation) at dilute condition while the system underwent gradual decrease of diffusion above semi-dilute concentration. With FPR and viscometry experiments, we revealed the probe behaviors in polyelectrolyte solution were strongly affected by the coil overlap concentration (0.5 g/L PAH concentration).

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.100.1-100.1
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• 2010

고효율 실리콘 양자점 태양전지를 제작하기 위해 Si과 C target을 co-sputtering 방식으로 제조한 SiC matrix를 열처리하여 박막 내에 Si nanocrystal들을 생성하였다. Si nanocrystal의 특성은 다양한 요인에 영향을 받는 데 barrier 물질인 SiC matrix가 가장 큰 영향을 준다. SiC는 900도 이상에서 열처리하는 동안 Si과 C과 SiC으로 재배열 혹은 재결합하는 데 이 때 가장 작은 carbon이 빠르게 diffusion하는 현상에 의해 Si nanocrystal의 성장과 특성에 영향을 주게 된다. 이 현상을 연구하기 위해 stoichiometric SiC/Si-rich SiC/stoichiometric SiC의 3층 구조로 시료를 제작하여 이를 SIMS의 depth profiling을 통하여 열처리 전보다 열처리 후에 Si-rich SiC layer내에 carbon이 약 2~3%정도 증가한 것으로 carbon이 diffusion된 것을 확인하였다. 이 시료를 UV-VIS-NIR spectroscopy, Raman, GIXRD 등의 다양한 측정을 통하여 carbon diffusion에 의한 Si nanocrystal의 특성변화를 연구하였다.

• Journal of Pharmaceutical Investigation
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• v.20 no.2
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• pp.79-88
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• 1990

A numerical model for diffusion and dissolution controlled transport from dispersed matrix is presented. The rate controlling process for transport is considered to be diffusion of drug through a concentration gradient coupled with time-dependent surface change and/or disappearance of the dispersed drug in response to the dissolution. The transport behavior of drug was explained in terms of ${\nu}$ parameter: ${\nu}$ value means a ratio of diffusion time constant and dissolution time constant. This general model has wide range of application from where release is controlled by the diffusion rate to where release is governed by the dissolution rate. Based on this model, theoretical drug concentration, particle size distributions in the polymer matrix system and the resulting release rate were also investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.553-556
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• 2006

Generally, concrete is one of the most widely used construction materials, because of its good durability to cost ratio. However, when subjected to severe environments its durability can significantly decline due to various harmful conditions. In this article, we would like to investigate a chloride ion diffusion of cement matrix with inert filler, which ground calcium carbonate(GCC). For the experimental results of the chloride ion diffusion, as the addition of GCC makes decreasing the permeability by micro-filler effect, the matrix of 5-15% ratio of replacement are superior to the GCC0 mortar matrix with respect to durability of cement matrix in this scope.

• Journal of Pharmaceutical Investigation
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• v.29 no.1
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• pp.7-12
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• 1999

The captopril matrix tablets composed of polyethylene oxide(PEO) was prepared and administered to beagle dogs. Captopril matrix tablets were prepared using direct compressed method and wet granulation compressed method with various ratios of drug to PEO. The diffusion rate of captopril matrix tablets followed on the Higuchi's diffusion model. With increasing hardness of captopril matrix tablets, release rate was decreased. Each formulation was evaluated by the area under the curve (AUC) and time course of plasma captopril concentration after oral administration to beagle dogs. The $AUC_{0-12}$ were $9.126\;{\mu}g\;h/ml$ and $6.417\;{\mu}g\;h/ml$ for the matrix tablets and conventional tablets, respectively. Therefore, the bioavailability of captopril matrix tablets was greater than that of commercial product. It is suggested that captopril matrix tablets using PEO is a useful sustained release formulation.

• Korean Journal of Materials Research
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• v.6 no.2
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• pp.210-220
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• 1996

The purpose of this study is to develop the processing techniques of Fiber Reinforced Metal by Liquid Phase Diffusion Bonding method with SiC fiber as a reinforcing material and CP Ti(Commercial Pure) as a matrix. The microstructure and the distribution of elements in reaction and CP Ti(Commercial Pure) as a matrix. The microstructure and the distribution of elements is reaction zone among CP Ti/Ti-15wt%Cu-20wt%Ni(TCN20)/SiC long fiber were investigated by Optical Microscope, SEM/EDX, EPMA, X-ray and AES. The results obtained in this study are as follows. 1) When Ti matrix composite materials are fabricated under the bonding condition of 1273Kx1200sec, the SiC long fiber was the most suitable reinforcing material for Ti matrix composite materials. 2) With SiC long fiber under same condition, a TiC layer(1.0-1.6$\mu\textrm{m}$) was observed on the surface of SiC long fiber. 3) Liquid Phase Diffusion Bonding has shown the feasibility of production of Ti matrix composite materials.

• Corrosion Science and Technology
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• v.18 no.3
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• pp.102-109
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• 2019

The hydrogen diffusion and trapping model with a numerical finite difference method (FDM) was modified and extended to accommodate $H_2S$ corrosion and scale forming processes of high-strength steel under tensile stress condition. The newly proposed diffusion model makes it possible to clearly understand combined effect of tensile stress and $H_2S$ corrosion process on hydrogen diffusion behaviors. The core concept of this theoretical approach is that overall diffusion behavior is separated into diffusion process through two respective layers: an outer sulfide scale and an inner steel matrix. Diffusion coefficient values determined by curve-fitting permeation data reported previously with the newly proposed diffusion model indicate that the application of tensile stress can contribute to continual increase in the diffusivity in the sulfide scale with a high density of defect. This suggests that the scale with a lower stability under the stress condition can be a key parameter to enhance hydrogen influx in the steel matrix. Consequently, resistance to hydrogen assisted cracking of the steel under tensile stress can be decreased significantly.

• Korean Journal of Materials Research
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• v.12 no.12
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• pp.955-961
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• 2002

2.7vol%TiNi/6061 Al composites with TiNi shape memory alloy as reinforcement were fabricated by vacuum hot press. It was investigated by OM, SEM, EPMA and XRD analysis for the behavior of diffusion layer formation on various heat treatment condition. Thickness of diffusion layer was increased proportionally according to heat treatment time. The layer was formed by the mutual diffusion of TiNi and Al. The diffusion rate from TiNi fiber to Al matrix was faster than that of reverse diffusion path. The more diffused layer was formed in Al matrix. The diffusion at interface layer was consisted of $A1_3$Ti, $Al_3$Ni analyzed by EPMA, XRD results.

• Korean Journal of Microbiology
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• v.28 no.3
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• pp.278-282
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• 1990

Diffusion and partition of progesterone into the polyacrylamide gel was examined. Diffusion coefficient of progesterone decreased down to an asymptotic value as the concentration of the organic solvents in the diffusing medium increased. However the partition coefficient diminished steadily. Crosslinking density in the gel didn't affected the diffusion coefficient considerably but lowered the partition coefficient due to the contraction of pore volume of the gel. Progesterone showed higher diffusion coefficient as well as partition coefficient in the polyurethane than in the polyacrylamide gel, which seems to be ascribed to the difference in hydrophobicity, pore volume and pore size of the polymer matrix.

• Corrosion Science and Technology
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• v.20 no.5
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• pp.295-307
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• 2021

Effects of ε-carbide (Fe_2.4C) on corrosion and hydrogen diffusion behaviors of ultra-strong steel sheets for automotive application were investigated using a number of experimental and analytical methods. Results of this study showed that the type of iron carbide precipitated during tempering treatments conducted at below A₁ temperatures had a significant influence on corrosion kinetics. Compared to a steel sample with cementite (Fe₃C), a steel sample with ε-carbide (Fe_2.4C) showed higher corrosion resistance during a long-term exposure to a neutral aqueous solution. In addition, the diffusion kinetics of hydrogen atoms formed by electrochemical corrosion reactions in the steel matrix with ε-carbide were slower than the steel matrix with cementite because of a comparatively higher binding energy of hydrogen with ε-carbide. These results suggest that designing steels with fine ε-carbide distributed uniformly throughout the matrix can be an effective technical strategy to ensure high resistance to hydrogen embrittlement induced by aqueous corrosion.